8 Acoustic Research Style Woofer for AR 4, 18, 22bx, 38b, 94, Others, W-850. Subwoofer Diameter: 8 Inches. Controller Type: Voice Control. Surround Sound Channel Configuration: 5. Number of Items: 1. Power Source: Corded Electric. Vehicle Service Type: Car. Package Dimensions: 10 x 10 x 7 inches. Audio Output Mode: Mono. Mounting Type: Flush Mount. 5 ohms for compatibility with 4 ohm and 8 ohm systems. Size: 8.25″ Hole cut-out: 7″ Depth: 3.3″ Voice coil: 1″, 4 layer, aluminum former Magnet: 10 oz. Impedance: 5 ohms, Re: 5.0 ohms Power: 50 watts RMS, 100 watts max Response: 40-5000 Hz Sensitivity: 91 dB, 1 watt, 1 meter. Fs: 48 Hz, Vas: 1.61 cu. Qms: 11.1, Qes. 86, Xmax: 4.6mm. Great replacement for many vintage 8 Advent woofers Made in USA. Fits:AR (Acoustic Research): 4a, 4ax, 4x, 6, 16, 18, 22BX, 38b, 94, 94r, 94S, 94Si, 94SX, 94X, Rock Partner, Spirit 142, Sprirt 162, TSW-210, TSW-410, 210067, 1210072, 1210097, 200037-0, and others.